1. Field of the Invention
The present invention relates generally to a method and a structure for improving the uniformity of light emitted from a backlight module, and more particularly to a method and a structure of splicing a plurality of small-size light guide plates (LGP) into a large-size LGP. Typically, when two adjacent small-size LGPs are spliced at a splicing portion, the splicing portion usually presents a dielectric index different from the small-size LGPs. As such, when the large-size splicing LGP emits light, the dielectric index difference would cause refraction of the light and presents a bright line at the splicing portion. The present invention is adapted for eliminating the bright lines caused at the splicing portions between adjacent small-size LGPs.
2. The Prior Arts
Liquid crystal displays (LCD) have been widely used by many electronic products, such as notebook computers, displays, cell phones, and LCD televisions. Typically, an LCD includes a backlight module providing a light source for displaying images. Therefore, backlight modules are necessary components for LCD products. Further, backlight modules are also employed in some non-LCD products which desire flat light emitting effects.
Generally, a conventional backlight module of an LCD includes an LGP and a light source. Some LCD televisions employ a bottom lighting structure in which a lamp is provided at a backside of the LGP serving as a light source. However, the LCD televisions employing such a structure would be dimensionally thicker. In order to obtain a thinner LCD television, a conventional technology is to employ light emitting diodes (LED) serving as the light source of the backlight module. In accordance with such a structure, a plurality of LEDs are provides at a lateral side of the LGP. A reflective sheet is provided at a first surface of the LGP. A second surface of the LGP positioned opposite to the first surface serves as a light emitting surface. A plurality of optical sheets including a diffusing sheet and a prism sheet are provided at the second surface of the LGP. The LEDs, the LGP, the reflective sheet, and the optical sheets are laminated together, and then formed by an outer frame. In operation, the LEDs project light entering the LGP from the lateral side. A part of the light is reflected by the reflective sheet. The light sequentially passes through the diffusing sheet and the prism sheet and is outputted thereby.
However, the LGP as foregoing discussed is an optical apparatus, which requires a very high optical precision and functionality. As such, a large-size LGP is often more difficult to fabricate than a small-size LGP, and thus has a higher fabrication cost. Hence, a conventional technology is to splice a plurality of small-size LGPs into a large-size LGP.
As shown in FIG. 1, there is shown a large-size splicing LGP structure constituted of two small-size LGPs 2. Each of the small-size LGPs 2 has at least one splicing edge A. The splicing edges A of the two small-size LGPs 2 are individually polished. Then, the splicing edges A of the two small-size LGPs 2 are spliced in close contact. An LED light source 2 is provided at a lateral side of each of the small-size LGPs 1. The LED light source 2 projects light into the small-size LGPs 1, the light is transmitted into the small-size LGPs 1, and is then outputted from an upper surface of the small-size LGPs 1, thus obtaining a flat light outputting performance as desired. However, the splicing portion of the two adjacent splicing edges A usually presents a dielectric index different from the bodies of the small-size LGPs 1. As such, when the light reaches the splicing portion, the dielectric index difference would cause refraction of the light and presents a bright line area B having a brightness higher than an average value at the splicing portion as shown in FIG. 2. In general, it causes a non-uniform brightness of the large-size LGP.